Ignition coil



Dec. 20, 1938. L. P. K'oNGsTED 2,141,141

IGNITION COIL Filed Dec. 27, 1957 ATTORNEY.

Patented Dec. 20, 1938 UNITED STATES PATENT` ori-ica IGNITION con.

Application December 27, 1937, Serial No. 181,937

7 Claims.

This invention relates to ignition coils, and particularly to ignitioncoils, preferably non-rotatable, for magneto electric generators andbattery' ignition systems in which'` the generating winding, usuallyprimary and secondary turns arranged either one outside the other,surrounds an outwardly projecting magnetic core usually o1 laminatedsheets of steel.

Ignition coils of this type contain superposed layers of turns ofenameled or other insulated wires separated between layers and betweenthe Aprimary and secondary sections by paper sheets or other insulatingmaterial, the entire coil sometimes being vacuum impregnated with waxwhich when molten flows into the winding of the coil, and when cooledhardens into a hard solid mass. It is known that oil of suitablegrade'is a better y insulation for high-voltagevacuum-impregnatdiillculty permanently.

ed ignition coils than is wax because the wax is' more or lesscrystalline when solidified, and therefore does not then fill all theinterstices of the paper or other insulation. But heretofore, while oil,being liquid, completely lilled the interstices of the coil at alltemperatures, it gradually escaped from the winding, particularly whenthe coil breathed upon being repeatedly subjected to heating and coolingin normal operation, and

coils sovtreated eventually lost some of their re-l sistance toelectrical breakdown. To reduce the amount' and rate of loss of the oil,the ignition coil is sometimes tightly taped and varnished by handaround the outside turns, and the end caps are machined and varnished,but this procedure is expensive without reliably It is a primary objectof my invention to provide a high voltage ignition 'coil which is filledor over-saturated with or in effect bathed in oil and which retains ahigh degree of resistance to Another object of my invention is toprovide Y an ignition coil with a casing which is substantially sealedagainst the entrancev of moisture and dust into the coil as welliasagainst the loss of oil from the co'il. .g

Another object of my invention is to. provide an ignition coil of thiskind which is inexpensive to manufacture and which is reliable inoperation over long periods of normal operation.

overcoming the (Cl. F-'361) These and other objects of my invention willbe apparent from the ensuing description of two modifications of myignition coil and from the separate layers are separated by a suitablein-.

sulation 5 as untreated linen or kraft paper sheets, the primary andsecondary sections being suitably insulated from each other by cardboardor the like. The insulation 5 between layers projects beyond 'the endturns of the layers, but

in my coils the extent of this projection may be less than formerlyonaccount of the high and permanent insulating property of the oilimpregnation hereinafter described. This entire.

coil structure is subjected to a temperature of 250 E. in a suitableimpregnating tank for approximately five hours, and then for severalWhile still under this vacuum, insulating oil of well known kind,preferably mineral, under'a'tmospheric pressure and at a tempera-ture ofabout 250 F., vis allowed to enter the tank to a level above the top ofthe coil Vand to remain there until all insulations are thoroughlyimpregnated, and all interstlces in the coil includ.`

.ing the paper between the layers o f turns and between the primary andsecondary sections, and

all spaces in andaround the laminated core, are.

assembly in a'housing which in the instance` sho/wn comprises apreformed cup-shaped member 6 of molded bakelite or bakelized paperhaving 'a central opening 'l vin the closed end 8 thereof. The centralopening l is slightly larger `than-theexternal dimensions of the core A,and

the tubular walls of the cup-shaped member 8 have an internal diametersomewhat larger than the external diameter ofthe coll to leave a smallspace therebetween for ease in assembly and to permit expansion of theoil within the casing under varying temperature conditions in normaloperation of the c oil. Prior to the insertion of the coil in thecup-shaped member, .a liberal. A

'amount of high melting point compound, the

properties of which are more fully described heref and I8 havingopenings I8 and 28 of slightly less inafter, is ilowed over one end ofthe coll from a heated tank. The coil I is then inserted into thehousing so that the core 4 projects through the opening 1, and ispressed down firmly into the casing so that the compound, still moltenor plastic, flows through all clearances between the core 4 and thesides of the opening, and also uniformly over that end of the coil, andpartly into the space between the outside periphery of the coil and thehousing. A layer of the same compound is then placed over the other endsurface of the coil, being applied liberally around the core 4 andaround the edge or rim of the cupshaped member 6. Before this compoundhas a chance to solidify, a preformed cover 9 with a central opening Ilikewise slightly larger than the core 4, and with the low tension leadII threaded through the opening I2 and the ground connection I3accommodated in the cutout I4, is pressed down firmly so that thecompound is squeezed into all spaces and interstices4 at and near thatend of the coil including the clearance between the rim of thecup-shaped member 6 and the edge of the cover 8 and also around the leadII and connection I3. The compound also lls the clearances between thecore and the edges of the opening I0. The cup-shaped member 8 isprovided with a hollow high tension terminal l (see Fig. 2) for thesecondary -wlnding of the coil and a low tension terminal connector I6for the primary winding. The openings of these terminals are suitablysealed with solderv after the leads are pulled tightly therethrough.After the compound has hardened at all these places, the coil is sealedin a fluid-tight manner so that substantially none of the oil with whichthe coil has been filled is lost even upon repeatedly 'reachingoperating temperatures as high as 220 F.

A compound which is of high melting point, that is one which will notsag from gravity below a temperature of 250 F., is used to preventsocalled cold ilcw at any temperature to which the coil is subjected innormal use. Also the compound is preferably of the kind which below thattemperature will not readily dissolve in, or chemically combine with,the oil with which the wound core is iilled. Preferably, a high meltingcoal tar rather than petroleum tar is used, and

a mineral ller or other inert material, such asl fullers earth, chalk ortalcum. may be mixed as a powder in the tar -to further raise the deforuse where the coil is placed in an exposed position. Where the coil isprotected, as for example by enclosure in a magneto housing, I preferthe construction shown in Fig. 2 in which the coil core is encased in ahousing of elastic material. Ordinary rubber isgnot suitable for thispurpose since it deteriorates when in contact with oil, but syntheticrubber, such as neoprene, thiokol land the like, does not deteriorate oncontact with oil and istherefore suitable for this purpose. As shown,two preformed cup-shaped members -II cross-sectional area than thecross-sectional area of the core 4 of the coil 2|-, are pressed over theassembled core and coil with the projecting end portions of the coreextending through the openings I9 and 20. The untreated coil windings ofthis construction are substantially the same as the ones previouslydescribed except that paper orl varnished silk washers 22, having adiameter slightly larger than the secondary coil, with square holespunched in the center thereof, are placed over each end thereof prior toinsertion in the cup-shaped members I1 and I8. These Washers act asprotective aprons which prevent the sealing compound from sealing theends of the paper layers between the windings. The cupshaped member IIis slightly longer than the cup-shaped member I8 and the edges of thecupshaped members overlap. and are united by sealing with a neoprene orsimilar rubber cement which is first liquid or plastic and latervulcanized by heat to form a duid-tight lap joint extendingcircumferentially around the coil. The openings in the housing at thecore, the high tension terminal I5, the grounding connection 24 and thelow tension wire 25 are originally of slightly less size than the partsthey surround so as to tightly grip them. The joints there are alsosealed with neoprene cement, thus forming a completely huid-tighthousing. The vulcanizing of the neoprene cement sealing all joints isaccomplished by baking the entire assembly for two hours at atemperature of 260 F.

In this embodiment of Fig. 2, the coil may be first impregnated with oilbefore its insertion in the elastichousing as described in connectionwith the structure shown in Fig. 1, but preferably the casing is filledwith oil after the housing structure has been vulcanized together andsealed as shown around the unimpregnated windings. In this latter case,the assembled coil structure is subjected to 'a vacuum impregnatingprocess at 250 F. and then filled with insulating oil as previouslydescribed. The oil-enters the casing through the opening 23 in the hightension terminal. As in the nrst embodiment, this hole is afterwardssealed by soldering.

This form provides an oil-tight elastic casing which permits thenecessary amount of expansion and contraction of the oil within thecasing under varying temperature conditions in normal operation of thecoil without loss of oil. I1' in the process of heating the oil in thecasing produces a pressure therein due to expansion of vapor, theelastic casing will expand slightly instead of permitting, the oil to beforced out through some of the joints. On cooling, the casing willcontract as the vapors condense, thus avoiding any tendency to drawexternal air and moisture into the casing.

Both constructions provide a structure in which the wires of. thesuperposed layers of the windings of the coil, the sheets of insulatingmaterial between the layers, and the core are filled with oil and inwhich t he casing is so sealed that the 2,141,141 when applied but whichhardens or is hardened after being squeezed into all open spaces andcooled, and which when hardened doesnot dissolve in or chemicallycombine with the insulating oil in the range of normal operatingtemperatures of the coil extending up to 220 F. Although there areherein described but tw embodiments of the invention other embodimentswithin the scope of the appended claims will be obvious to those skilledin the art from a consideration of. the forms shown. For instance, itwill be obvious that the coil winding with its core may be vacuumtreated under heat, filled with oil as aforesaid and then completelysealed in duid-tight manner in a metal or other container by insulatingmaterial like that described in connection with the rst embodiment whichhas a comparatively high temperature of cold ow but whichvmelts at asuitably high temperature. Such ignition coils are particularly adaptedfor present battery ignition coils of well known forms which haveinsulating caps and no core portions projecting outside the containers,as for instance the type shown in Ehrlich et al. U. S. Patent No.1,977,122.

Having thus described my invention, what I claim is:

1. A high-voltage ignition coil comprising win'dings of superposedlayers of insulated wires; insulating sheets between said layers; a corefor said coil; insulating oil lling the interstices of and the openspaces in and between said wires, sheets and core; and a fluid-tightcasing comprising two preformed members of oil-resistant materialsurrounding said windings, each of said members forming an end Wall ofthe casing and each of said end walls having a central aperturetherethrough through which an end of the core projects; said casingbeing duid-sealed interiorly at the joints between said end portions andsaid core with a material which below 220 F. does not flow or dissolvein or chemically combine with said insulating oil.

2. A high-voltage ignition coil comprising windings of superposed layersof insulated wires; insulating sheets between said layers; a core forsaid coil; insulating oil lling the interstices of and the open spacesin and between said wires, sheets and core; and a huid-tight casingcomprising two preformed members of oil-resistant material surroundingsaid windings, each of said members forming an end wall of the vcasingand each of said end walls having a central aperture therethroughthrough which an end of the core projects; said casing being huid-sealedinteriorly at the joints between said end portions and 'said core withla tar product of high cold ow temperature which has an inert ller.

3. A high-voltage ignition coil comprising windings of superposed layersof insulated wires; insulating sheets between said layers; a core forsaid coil havingend portions projecting therefrom; insulating oilfilling the interstices of and the open spaces in and between saidwires, sheets and core; and a fluid-tight casing comprising twopreformed members of oil-resistant material surrounding said windings,each of said members forming an apertured end wall through which saidend portions of the core project; said casing being fluid-sealedinteriorly at the joints between said end portions and said core with amaterial which below 220 F. doesv not flow or dissolve in or chemicallycombine with said insulating oil.

4. A high voltage ignition coil comprising windings ofsuperposed layersof insulated wires; insulating sheets between said layers; a core forsaid coil having end portions projecting therefrom; insulating oil llingthe interstices of and the open spaces in and between said wires, sheetsand core; and a non-metallic fluid-tight casing comprising two preformedmembers of oil-resistant material surrounding said windings each of saidmembers forming an apertured end wall through which said end portions ofthe coreproject; said casing being fluid-sealed interiorly at the jointsbetween said end portions and said core with a material which below 220F. does not ilow or dissolve in or chemically combine with saidinsulating oil.

5. A high-voltage ignition coil comprising windings of superposed layersof insulated wires; insulating sheets between said layers; a core forsaid coil; insulating oil lling the intersticesof and the open spaces inand between said wires, sheets and core; and an elastic oil-resistantcasing comprising two preformed members surrounding said windings, eachof said members forming an end wall of the casing and each of said endwalls having a central aperture therethrough through which an end of thecore projects; said casing being fluid-sealed interiorly at the jointsbetween said end portions and said core with a material which belowv 220F. does not ow or dissolve in or chemically combine withsaid insulatingoil.

6. A high-voltage ignition coil comprising windings of superposed layersof insulated wires; insulating sheets between said layers, a core forsaid coil having end portions projecting therefrom; insulating oilfilling the interstices of and the open spaces in and between saidwires, sheets and core; an elastic oil-resistant casing comprising twopreformed members surrounding said windings, each of said membersforming an apertured end wall through which said end portions project;and, extending through said casing from said winding, a sealed-offhollow high-voltage terminal which, when open, forms a passage, forinsulating oil to the interior of said casing; said casing beingHuid-sealed interiorly at the joints between said end portions and saidcore with a material which below 220 F. does not ow or dissolve in orchemically combine with said insulating oil.

7. A high-voltage ignition -coil comprising windings of superposedlayers of insulated wires; insulating sheets between` said layers, acore for said coil having end portions projectingv therefrom; insulatingoil filling the interstices of and the open spaces in and between saidwires, sheets and core; and a fluid-tight casing comprising twopreformed members of elastic material surrounding said windings each ofsaid members forming an apertured end wall with openings of slightlysmaller area than the cross-sectional area of said end portions of thecore, whereby said elastic material grips tightly the projectingportions of the core when the latter are inserted into said openings;said casing being fluid-sealed interiorly at the joints between said endportions and said corev with a material which below 220 F. does not tlowor dissolve in or chemically combine with said insulating oil.

LUDVIG P. KONGSTED.

